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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Audio/Video Transport Working Group A. Clark 3 Internet-Draft Telchemy 4 Intended status: Standards Track G. Zorn 5 Expires: June 17, 2013 Network Zen 6 Q. Wu 7 Huawei 8 December 14, 2012 10 RTP Control Protocol (RTCP) Extended Report (XR) Block for Discard Count 11 metric Reporting 12 draft-ietf-xrblock-rtcp-xr-discard-10.txt 14 Abstract 16 This document defines an RTP Control Protocol(RTCP) Extended Report 17 (XR) Block that allows the reporting of a simple discard count metric 18 for use in a range of RTP applications. 20 Status of this Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on June 17, 2013. 37 Copyright Notice 39 Copyright (c) 2012 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 1.1. Discard Count Report Block . . . . . . . . . . . . . . . . 3 56 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 57 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 58 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5 61 3. Discard Count Metric Report Block . . . . . . . . . . . . . . 6 62 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 63 3.2. Definition of Fields in Discard Count Metric Report 64 Block . . . . . . . . . . . . . . . . . . . . . . . . . . 6 65 4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 9 66 4.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 9 67 4.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 9 68 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 69 5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 10 70 5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 10 71 5.3. Contact information for registrations . . . . . . . . . . 10 72 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 73 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12 74 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 75 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 76 9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 77 9.2. Informative References . . . . . . . . . . . . . . . . . . 14 78 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 15 79 A.1. draft-ietf-xrblock-rtcp-xr-discard-10 . . . . . . . . . . 15 80 A.2. draft-ietf-xrblock-rtcp-xr-discard-09 . . . . . . . . . . 15 81 A.3. draft-ietf-xrblock-rtcp-xr-discard-08 . . . . . . . . . . 15 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 84 1. Introduction 86 1.1. Discard Count Report Block 88 This document defines a new block type to augment those defined in 89 [RFC3611] for use in a range of RTP applications. The new block type 90 supports the reporting of the number of packets which are received 91 correctly but are never played out, typically because they arrive too 92 late to be played out (buffer underflow) or too early (buffer 93 overflow). The metric is applicable both to systems which use packet 94 loss repair techniques (such as forward error correction [RFC5109] or 95 retransmission [RFC4588]) and to those which do not. 97 This metric is useful for identifying the existence, and 98 characterizing the severity, of a packet transport problem which may 99 affect users' perception of a service delivered over RTP. 101 This block may be used in conjunction with [BGDISCARD] which provides 102 additional information on the pattern of discarded packets. However 103 the metric in [BGDISCARD] may be used independently of the metrics in 104 this block. 106 In case of Discard count metric block sent together with Burst gap 107 discard metric block defined in [BGDISCARD] to the media sender or 108 RTP based network management system, information carried in the 109 discard count metric block and Burst gap discard metric block allows 110 them calculate the some bust gap summary statistics, e.g., gap 111 discard rate. 113 The metric belongs to the class of transport-related end system 114 metrics defined in [RFC6792]. 116 1.2. RTCP and RTCP XR Reports 118 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 119 defined an extensible structure for reporting using an RTCP Extended 120 Report (XR). This document defines a new Extended Report block for 121 use with [RFC3550] and [RFC3611]. 123 1.3. Performance Metrics Framework 125 The Performance Metrics Framework [RFC6390] provides guidance on the 126 definition and specification of performance metrics. The RTP 127 Monitoring Architectures [RFC6792] provides guideline for reporting 128 block format using RTCP XR. The Metrics Block described in this 129 document are in accordance with the guidelines in [RFC6390] and 130 [RFC6792]. 132 1.4. Applicability 134 This metric is believed to be applicable to a large class of RTP 135 applications which use a jitter buffer. 137 Discards due to late or early arriving packets affects user 138 experience. The reporting of discards alerts senders and other 139 receivers to the need to adjust their transmission or reception 140 strategies. The reports allow network managers to diagnose these 141 user experience problems. 143 The ability to detect duplicate packets can be used by managers to 144 detect network layer or sender behavior which may indicate network or 145 device issues. Based on the reports, these issues may be addressed 146 prior to any impact on user experience. 148 2. Terminology 150 2.1. Standards Language 152 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 153 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 154 document are to be interpreted as described in RFC 2119 [RFC2119]. 156 In addition, the following terms are defined: 158 Received, Lost and Discarded 160 A packet shall be regarded as lost if it fails to arrive within an 161 implementation-specific time window. A packet that arrives within 162 this time window but is too early or late to be played out or 163 thrown away before playout due to packet duplication or redundancy 164 shall be regarded as discarded. A packet shall be classified as 165 one of received (or OK), discarded or lost. The Discard Count 166 Metric counts only discarded packets. The metric "cumulative 167 number of packets lost" defined in [RFC3550] reports a count of 168 packets lost from the media stream (single SSRC within single RTP 169 session). Similarly the metric "number of packets discarded" 170 reports a count of packets discarded from the media stream (single 171 SSRC within single RTP session) arriving at the receiver. Another 172 metric defined in [RFC5725] is available to report on packets 173 which are not recovered by any repair techniques which may be in 174 use. 176 3. Discard Count Metric Report Block 178 Metrics in this block report on the number of packets discarded in 179 the stream arriving at the RTP end system. The measurement of these 180 metrics is made at the receiving end of the RTP stream. Instances of 181 this Metrics Block refer by SSRC to the separate auxiliary 182 Measurement Information block [RFC6776] which contains measurement 183 intervals. This metric block relies on the measurement interval in 184 the Measurement Information block indicating the span of the report 185 and should be sent in the same compound RTCP packet as the 186 measurement information block. If the measurement interval is not 187 received in the same compound RTCP packet as this metric block, this 188 metric block should be discarded. 190 3.1. Report Block Structure 192 0 1 2 3 193 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 194 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 195 | BT=PDC | I |DT | resv.| block length = 2 | 196 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 197 | SSRC of Source | 198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 199 | number of packets discarded | 200 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 202 Figure 1: Report Block Structure 204 3.2. Definition of Fields in Discard Count Metric Report Block 206 Block type (BT): 8 bits 208 A Discard Count Metric Report Block is identified by the constant 209 PDC. 211 [Note to RFC Editor: please replace PDC with the IANA provided 212 RTCP XR block type for this block.] 214 Interval Metric Flag (I): 2 bits 216 This field indicates whether the reported metric is an interval, 217 cumulative, or sampled metric [RFC6792]. The Discard Count Metric 218 can only be measured over definite intervals, and cannot be 219 sampled. Accordingly, the value I=01, indicating a sampled value, 220 MUST NOT be used. The value I=00 is reserved for future 221 definition, and MUST NOT be used. 223 Discard Type (DT): 2bits 225 This field is used to identify the discard type used in this 226 report block. The discard type is defined as follows: 228 00: Report packet discarded or being thrown away before playout 229 due to packets duplication. 231 01: Report packet discarded due to too early to be played out. 233 10: Report packet discarded due to too late to be played out. 235 The value DT=11 is reserved for future definition and MUST NOT be 236 used. 238 An endpoint MAY report only one of the above three discard types 239 blocks in an compound RTCP report in a reporting interval. It MAY 240 also report a combination of any two discard types in a compound 241 RTCP report. The endpoint MAY report duplicate packet discard 242 (DT=0) block with the other two discard (DT=1, 2) blocks. 244 Some systems send duplicate RTP packets for robustness or error 245 resilience. This is NOT RECOMMENDED since it breaks RTCP packet 246 statistics. If duplication is desired for error resilience, the 247 mechanism described in [RTPDUP] can be used, since this will not 248 cause breakage of RTP streams or RTCP statistics. 250 Reserved (resv): 4 bits 252 These bits are reserved. They MUST be set to zero by senders and 253 ignored by receivers. 255 block length: 16 bits 257 The length of this report block in 32-bit words, minus one and 258 MUST be set to 2,, in accordance with the definition of this field 259 in [RFC3611]. The block MUST be discarded if the block length is 260 set to a different value. 262 SSRC of source: 32 bits 264 As defined in Section 4.1 of [RFC3611]. 266 number of packets discarded: 32 bits 268 Number of packets discarded over the period (Interval or 269 Cumulative) covered by this report. 271 If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE 272 MUST be reported to indicate an over-range measurement. If the 273 measurement is unavailable, the value 0xFFFFFFFF MUST be reported. 275 Note that the number of packets expected in the period associated 276 with this metric (whether interval or cumulative) is available 277 from the difference between a pair of extended sequence numbers in 278 the Measurement Information block [RFC6776], so need not be 279 repeated in this block. 281 4. SDP Signaling 283 [RFC3611] defines the use of SDP (Session Description Protocol) 284 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 285 without prior signaling. 287 4.1. SDP rtcp-xr-attrib Attribute Extension 289 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 290 in [RFC3611] by providing an additional value of "xr-format" to 291 signal the use of the report block defined in this document. 293 xr-format =/ xr-pdc-block 295 xr-pdc-block = "pkt-dscrd-count" 297 4.2. Offer/Answer Usage 299 When SDP is used in offer-answer context, the SDP Offer/Answer usage 300 defined in [RFC3611] for unilateral "rtcp-xr" attribute parameters 301 applies. For detailed usage in Offer/Answer for unilateral 302 parameter, refer to section 5.2 of [RFC3611]. 304 5. IANA Considerations 306 New block types for RTCP XR are subject to IANA registration. For 307 general guidelines on IANA considerations for RTCP XR, refer to 308 [RFC3611]. 310 5.1. New RTCP XR Block Type value 312 This document assigns the block type value PDC in the IANA "RTCP XR 313 Block Type Registry" to the "Discard Count Metrics Block". 315 [Note to RFC Editor: please replace PDC with the IANA provided RTCP 316 XR block type for this block.] 318 5.2. New RTCP XR SDP Parameter 320 This document also registers a new parameter "pkt-dscrd-count" in the 321 "RTCP XR SDP Parameters Registry". 323 5.3. Contact information for registrations 325 The following contact information is provided for all 326 registrations in this document: 328 Qin Wu (sunseawq@huawei.com) 330 101 Software Avenue, Yuhua District 331 Nanjing, Jiangsu 210012 332 China 334 6. Security Considerations 336 It is believed that this proposed RTCP XR report block introduces no 337 new security considerations beyond those described in [RFC3611]. 338 This block does not provide per-packet statistics so the risk to 339 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 340 does not apply. 342 7. Contributors 344 Geoff Hunt wrote the initial draft of this document. 346 8. Acknowledgments 348 The authors gratefully acknowledge reviews and feedback provided by 349 Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, 350 Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, 351 Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, 352 Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi 353 Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada,Kevin 354 Gross, Varun Singh, Claire Bi, Roni Even, Dan Romascanu. 356 9. References 358 9.1. Normative References 360 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 361 Requirement Levels", March 1997. 363 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 364 Applications", RFC 3550, July 2003. 366 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 367 Protocol Extended Reports (RTCP XR)", November 2003. 369 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 370 Description Protocol", July 2006. 372 9.2. Informative References 374 [BGDISCARD] 375 Hunt, G., "RTCP XR Report Block for Burst Gap Discard 376 metric Reporting", 377 ID draft-ietf-xrblock-rtcp-xr-burst-gap-discard-06, 378 October 2012. 380 [RFC4588] Rey, J., "RTP Retransmission Payload Format", RFC 4588, 381 July 2006. 383 [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error 384 Correction", RFC 5109, July 2006. 386 [RFC5725] Begen, A., "RTCP XR Report Block for Post-Repair Loss 387 metric Reporting", RFC 5725, February 2010. 389 [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric 390 Development", RFC 6390, October 2011. 392 [RFC6776] Hunt, G., "Measurement Identity and information Reporting 393 using SDES item and XR Block", RFC 6776, October 2012. 395 [RFC6792] Wu, Q., "Monitoring Architectures for RTP", RFC 6792, 396 November 2012. 398 [RTPDUP] Begen, A. and C. Perkins, "Duplicating RTP Streams", 399 ID draft-ietf-avtext-rtp-duplication-00, July 2012. 401 Appendix A. Change Log 403 Note to the RFC-Editor: please remove this section prior to 404 publication as an RFC. 406 A.1. draft-ietf-xrblock-rtcp-xr-discard-10 408 The following are the major changes compared to previous version: 410 o Editorial change to get in line with recently discussed drafts. 412 o Remove DT=3 based on the discussion to summary statistics draft. 414 A.2. draft-ietf-xrblock-rtcp-xr-discard-09 416 The following are the major changes compared to previous version: 418 o SDP Duplicated Parameter Deleting. 420 A.3. draft-ietf-xrblock-rtcp-xr-discard-08 422 The following are the major changes compared to previous version: 424 o Outdated reference update. 426 o Editorial changes based on comments that applied to PDV and Delay 427 drafts. 429 Authors' Addresses 431 Alan Clark 432 Telchemy Incorporated 433 2905 Premiere Parkway, Suite 280 434 Duluth, GA 30097 435 USA 437 Email: alan.d.clark@telchemy.com 439 Glen Zorn 440 Network Zen 441 77/440 Soi Phoomjit, Rama IV Road 442 Phra Khanong, Khlong Toie 443 Bangkok 10110 444 Thailand 446 Phone: +66 (0) 87 502 4274 447 Email: gwz@net-zen.net 449 Qin Wu 450 Huawei 451 101 Software Avenue, Yuhua District 452 Nanjing, Jiangsu 210012 453 China 455 Email: sunseawq@huawei.com